Nutrition Action November 2010 : Page 4
Peak Bone Mass Bone Mass Menopause Above the fracture threshold, bones shrug off minor stress Below the fracture threshold, it doesn’t take much stress to break a bone Fracture Threshold Age 15 30 50 65 A drop in estrogen leads to a decline in bone mass after menopause. Adequate calcium, vitamin D, fruits, vegetables, and exercise can help keep bone mass from falling below the fracture threshold. That’s the zone in which a hip, spine, or wrist is more likely to break. Q: Are you saying that protein is bad for bones? A: No.Many adults aren’t getting the amount of protein that most of us think is needed. The Recommended Dietary Al-lowance is 0.8 grams of protein per kilo-gram of body weight, but 1.0 or 1.1 grams per kilogram seems to be associated with slower muscle wasting in older people. There’s not fi nal proof, but the evidence is compelling. So cutting protein to lower acid load can be counterproductive to individuals with marginal protein intake. Instead, we need to cut back on grain foods. In an obese population, to get rid of some of these grains—which are calorie-laden and acid-producing—would be the ticket. Q: What’s the next step in your re-search? A:We want to do a longer, three-year trial, with hard endpoints like muscle size, muscle performance, rates of bone loss, etc. But fi rst we need to make sure that we are using the optimal dose of potassium bicarbonate.We are trying to get a dose-ranging study approved and done so that we can do the big trial with the best dose. WHAT’S YOUR FRAX? You can use the FRAX (Fracture Risk Assessment Tool) to estimate your risk of fracture, whether or not you’ve had your bone mineral density (BMD) tested. The National Osteoporosis Foundation Guide recommends that doctors consider prescribing medication if your risk of a hip fracture is at least 3 percent—or your risk of any major bone fracture is at least 20 percent—over the next 10 years. Most women (and men) do not cross either of those thresholds until their 70s. A typical 65-year-old woman— like Wanda B. Strong—would need medication only if she had a previous fracture due to mild trauma (like falling from stan-ding height, not as the result of a car crash), or if she had taken glucocorticoids (like prednisolone) for more than three months, or if she had rheumatoid arthritis (not osteoarthritis), or if she had secondary osteoporosis (a condi-tion—like menopause before age 45 or Type 1 diabetes—that is strongly linked to osteoporosis). To calculate your FRAX score, go to www.sheffi eld.ac.uk/FRAX and click on Calculation Tool. 4 NUTRITION ACTION NOVEMBER NUTRITION ACTION NOVEMBER ■ NOVEMBE NOVEMBER 2010 MBER 2 0 10 Unfortunately, that isn’t always done. With vitamin D, for example, trials have used different doses. There are no dose comparisons that would enable you to make an educated guess at the best dose. So now—millions and millions of dollars later—we are left trying to infer what the best vitamin D dose would be. It’s waste-ful to do it that way. But getting funding to test doses is so grindingly slow. Q: Would you recommend that people consume bicarbonate? A: No. I would advise people to eat fruits and vegetables.We’re studying potassium bicarbonate because we know pre-cisely how much acid it neutralizes. VITAMIN D Q: What other nutrients are linked to both muscle and bone? A: Vitamin D. It improves strength in the legs and lowers the risk of falling. Second, it improves bone strength, so it lowers the risk of your having a fracture should you fall. Q: How does it work? A: Vitamin D is essential for the absorption of calcium, which is needed for bone. Animals that are totally vitamin-D-deficient can-not form bone and can’t remodel bone. [See “Super Remodel,” p. 6.] Inadequate D levels are associated with more rapid bone loss and more fractures, no question. Q: How does vitamin D affect muscle? A: That’s not as thoroughly under-stood at the cellular and molecular level. There are vitamin D receptors 80 Illustration: Loel Barr.